EVALUATION OF POLYSORBATE 20 AS CORROSION INHIBITOR FOR MILD STEEL IN ACIDIC MEDIUM AND THE SYNERGISTIC EFFECT OF A CONDUCTING POLYMER, POLYETHOXYANILINE.

Polysorbate 20 (Poly-20) was evaluated as a corrosion inhibitor for mild steel (MS) in 0.5M sulfuric acid by weight loss and polarization techniques at different concentrations and temperatures. The inhibition efficiency increases with the decrease in concentration and was found to be maximum at 0.25% (v/v).The Nyquist plots were used to get the values of R_s (series resistance) and C_dl (double layer capacitance). The corrosion data has been analysed to determine the surface coverage at different temperatures. The heat of adsorption values, Q_ads and the effective activation energy values, E_eff has been reported. Poly-20 follows El-Awady adsorption isotherm. The effect of Polyethoxyaniline (PEA), a conducting polymer mixed with equal volume of Poly-20 (0.25%(v/v) on the corrosion inhibition of mild steel in 0.5M sulfuric acid has also been investigated. The inhibition efficiency was found to higher with the conducting polymer solution than in Poly-20. The surface morphology of mild steel samples in absence and presence of PEA in Poly-20 were also examined using Scanning Electron Microscopy. Quantum chemical analysis of the inhibitors was carried out to supplement the results obtained from various other techniques.